5. What are the main types of seismic waves?

Seismic waves can be divided into two groups based on their passage through the Earth's body.

(1)

Body waves: Waves that travel inside the Earth's interior. According to the wave property these waves can be divided into the following two classes:
(i) P-waves (primary wave, longitudinal or pressure wave): They are similar to sound waves. The particles vibrate along or parallel to the direction of wave propagation. These are the fastest waves.
(ii) S-waves (shear wave, secondary wave, or transverse wave): The particles vibrate perpendicular to the direction of the wave propagation. The vibration shakes horizontally and the velocity of the S-waves is next to that of the P-waves as they pass through the same medium.

(2)

Surface waves: Waves that travel along the Earth's surface and the layers near the surface. These waves can generally be divided into the following two classes:
(i) Love waves: The particles vibrate on a horizontal plane and perpendicular to the direction of wave propagation.
(ii) Rayleigh waves: The particles vibrate on a vertical plane and follow a retrograde ellipse.

When the seismic waves pass the medium, their particle motions are shown as in the diagram above.